*Changes in sediment provenance and oceanography across the Denmark Strait over the last 2000 cal yr BP: An ongoing study

1 University of Colorado2 University of South Florida3 Plymouth University4 Plymouth University5 Old Dominion University6 University of Florida7 University of Colorado8University of Icelan

Event

42nd International Arctic Workshop

7-9 March 2012

Winter Park, Colorado

Abstract

The area of the Denmark Strait is a “type area” for the generally
accepted climatic intervals of the last 2000 cal yr BP, including the
Medieval Warm Interval (MWI) and the Little Ice Age (LIA). On the N
Iceland shelf, the 2000 cal yr BP interval marks a dramatic change in
benthic foraminifera, with the arctic species Elphidium clavata forma
clavata, making a dramatic re-appearance. Paleoceanographic proxy data
from 5 cores, resampled at 100-yr intervals, from SW, NW, and N Iceland
showed a coherent response between a variety of proxies, including
ice-rafted minerals, the sea ice biomarker IP25, carbonate weight%, and
foraminiferal light stable isotopes (Axford et al., 2011) (Fig. 1). The
1st PCA explains 68% of the variance in the data, and is positively
associated with quartz wt% and IP25, and is negatively loaded with
carbonate values. Here we extend this analysis across the Denmark
Strait to the more polar environment of East Greenland between Scoresby
Sund and Kangerlussuaq Trough (~66°-70°N) (Fig. 2) with a multi-proxy
approach including 210Pb and 137Cs dating (Jaeger), foraminifera and
their light isotopes (Jennings and Olafsdottir), Fe-iron oxide
provenance fingerprinting (Darby), lithic counts (Alonso-García),
sea-ice biomarkers and total organic carbon content (Cabedo Sanz and
Belt), and X-ray diffraction and sediment magnetic mineral composition
(Andrews). Data analysis is still ongoing on several of the proxies.
Along the NW and N Iceland shelf, drift-ice is a frequent but not
pervasive element in the environment, whereas in contrast, the East
Greenland shelf is characterized by an extensive and pervasive cover of
sea ice (~October to July ±), including landfast sea-ice, and with
numerous tidewater glacier margins contributing icebergs. Kangerlussuaq
Trough and Fjord, a focus of the research, is directly influenced by
modified Atlantic Water, which forms an Intermediate Water mass linked
to the Irminger Current (Jennings et al., 2011).
We have extended our research onto the East Greenland and Iceland shelf
using a number of high-resolution cores from the PO175, HU93030, JM96-,
B997- and MD99- cruises. On the NW/N Iceland shelf we also present data
on a series (4) of small 20-cm gravity cores collected in 1997.
Chronological control is being based on AMS 14C dates, 210Pb and 137Cs
(Smith et al., 2002). Three short giant gravity cores (~20 cm in length)
(PO175GKC#7, -8, and –9) in the middle reaches of Kangerlussuag Trough
extend back into the middle of the Little Ice Age, whereas on the inner
shelf HU93030-019B and MD99-2322 can be combined to present a detailed
record of environmental change over the last 2000 cal yr (Fig. 3), which
can then be directly compared with data from the MD99-2263 box core
(Andrews et al., 2009). Rates of sediment accumulation vary by a factor
of 10 between the East Greenland (~0.2cm/yr) versus Iceland (0.02cm/yr)
margins across the strait. These rates allow multi-decadal to
century-scale resolution of sediment archives.
The data for the last ~190 yrs in the PO175GKC cores can be compared
with the historical (Schmith and Hanssen, 2003) compilation of the
Storis records (ice transported around the southern tip of Greenland and
north along the SW/W Greenland margin). The wealth of data that are
accumulating for this cross-strait transect will be assessed to answer
the following critical questions: 1) are the climate events (based on
our proxies) on either side of Denmark Strait strongly correlated? 2)
Can these events be strongly linked to the “standard” LIA, MWI, Dark
Ages, and Roman Warm Period intervals? 3) Can we detect significant
temporal variations in our proxies that deal with sediment provenance?
4) What are the associations, if any, between sediment and biological
proxies?

Smith, L.M., Alexander, C., Jennings, A.E., 2002, Accumulation in
East Greenland Fjords and on the continental shelves adjacent to the
Denmark Strait over the last century based on 210Pb geochronology.
Arctic, v. 55, p. 109-12